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133

PLASTICS IN FOOD PACKAGING

PACKAGING ASPECTS OF BEVERAGES:CARBONATED AND NON-CARBONATED

Chapter

7PACKAGING ASPECTS OF

BEVERAGES: CARBONATEDAND NON-CARBONATED

K R Kumar

Food Packaging Technology DepartmentCentral Food Technological Research Institute

Mysore 570 020 (INDIA)

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PACKAGING ASPECTS OFBEVERAGES: CARBONATED

AND NON-CARBONATED

IntroductionAccording to the Fruit Products Order

(FPO) 1955, fruit beverage or fruit drinkmeans any beverage or drink which ispurported to be prepared from fruit juice andwater or carbonated water and containingsugar, dextrose, invert sugar or liquidglucose. The minimum percentage of fruit

juice in the final product shall be not lessthan 5 percent. Fruit syrup connotessweetened fruit juice of not less than 25percent of fruit juice.

RTS fruit beverages should haveminimum of not less than 10% of fruit juiceand total soluble solids in the final product.Similar specifications have been cited forfruit crush, squash, cordial, unsweetenedand sweetened juice, nectar andconcentrate.

The Standards of Weights and Measures(Packaged Commodities) Rules 1977 specify(The Third Schedule) quantities in whichaerated soft drinks and non-alcoholicbeverages to be packed as: 100 ml, 150 ml,

200 ml, 250 ml, 300 ml, 330 ml (in cans only),500 ml, 750 ml, 1 litre, 1.5 litres, 2 litres andthereafter in multiples of 1 litre upto 5 litres.

The requirements of packages intended

to contain fruit beverages are:i) Absolutely leak proof and prevent

contamination.

ii) To protect the contents againstchemical deterioration.

iii) No pickup of external flavours.

iv) Be hygienic and safe.

v) To retain carbonation in carbonatedbeverages.

vi) Economical, easy to use anddisposable.

Processing Aspects

The traditional packaging procedure forfruit beverages involved heating the de-aerated juice to 90-95°C in heat-exchanger,filling the hot liquid directly into containers,sealing and inverting the cans, holding themfor 10-20 minutes and subsequent cooling.This hot-fill-hold-cool process ensured thecommercial sterility for the products. Theuse of glass container with suitable closuresor acid-resistant (AR) lacquered tin plate

cans was practiced.The use of glass bottles for the packaging

of fruit beverages was widespread althoughthe hot-fill/hold/cool process had to be

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applied with care to avoid breakage of the

containers. Glass is still the preferredpackaging medium for high quality fruitbeverages. However, in recent years, anincreasing proportion is being packagedaseptically.

The improvements that have taken placein glass bottle packaging are:

i) Light weight.

ii) Surface coating to increase abrasionresistance.

iii) Use of wide mouth containers fitted

with easy-open-end (EOE) caps.

Metal Containers

Tinplate cans which are made of lowcarbon mild steel of 99.75 purity strip,coated with tin either by dipping orelectrolytical plating are suitable. Doublereduced (DR) tinplate, with a second coldreduction treatment given, is widely used.

The three-piece cans have body and oneend in steel-base and the other end fittedwith an aluminium EOE, while two-piece

cans have an integral body and bottom andtop fitted with an EOE lid. The two-piececan has been claimed to be more economicaldue to savings in the use of metal, solder,etc., but its greatest technical advantagesare the elimination of bottom double seamand the side seam and improved lacqueringsystem.

Tin-free-steel (TFS) or ectrolyticallychrome coated steel (ECCS) cans withadhesive bonded side seams also serve asbeverage containers.

Fruit and vegetable juices packed andstored in aluminium cans with 21-26 inchof vacuum cause severe corrosion, hencelacquered cans should be used. The corrosion

rate is dependent on the nature of organic

acids present and the buffering capacity ofthe contents rather than the acidity. It hasbeen shown that apple beverage storedfor 22 months in aluminum can wascomparable to other types of containers.

Easy-Open-Ends

The easy-open-ends used for beveragecontainers are made on one press from twosets of aluminium feed stock. The shell ismade and scored in a normal pressoperation and a second strip of aluminium

is later fed when the integral rivet is stampedin the centre of the end. The strip is stampedinto a ring and is fitted over the rivet. Theelongated scored area is removed when thering is lifted and pulled back.

A non-detachable tab EOE is preferredsince litter problem can be solved. Thus anumber of types of ‘environment friendly’ends have been developed.

Plastic Containers

Over the years, many types of plastic

containers have been developed to packagefruit beverages. The three types that haveappeared are (i) Plastina-plastocan, (ii)

Merolite and (iii) Rigello bottle.

Plastina

This type of container is made up of threecomponents – (a) a two ply body material, (b)an outer container intended for use as adrinking cup and (c) an aluminium EOE.The Plastina can is represented by a majoradvance in processing in the developmentof co-extrusion system in which plies could

be separated easily. This could reduce oneof the major constraints in the use of laminateswhich could eliminate the inability toreprocess the scrap.

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Merolite System

This container, developed in UK, consistsof a film laminate based on orientedpolyvinylidene chloride-coated polye-thylene terephthalate (PET) made up oftubular packages. The container consistedof a lid opened by tearing off a strip ofplastic covering a series of pouring holes.

The comparative efficiencies of differenttypes of containers including plasticpouches in the retention of vitamin C inorange juice is shown in Table 7.1.

It has been shown that ascorbicacid (vitamin C) content in natural orange

Table 7.1. Ascorbic acidretention in orange beverage

Package % retention

1 m 2 m 3 m

Metal can 95 85 80

Glass bottle 93 80 78

Al-foil laminate pouch 93 78 75PET-bottle 78 65 62

Standi pack (PA based) 65 52 50

beverage packed in aluminum foil linedpouches was comparable to that packed intinplate containers while metallized

polyester/ polyethylene pouches indicated

lesser retention, especially at highertemperatures (Table 7.2).

Permeability to oxygen is the most criticalfactor in determining the shelf life ofaseptically packed beverages. This explainswhy storage temperature plays an importantrole in maintaining the quality of products.Flexible packages offer economic savingsover conventional glass and metal containers,but for the most part, are permeable to oxygen.Therefore, it critical to select a flexible packagethat minimizes the permeability to oxygen.

Ascorbic acid loss in packs of variouspackaging materials with differenttransmission rates indicate the importanceof selecting proper flexible package barrier(Table 7.3).

ASEPTIC PACKAGING

Functional Requirements ofAseptic Packages

1. High impermeability to water-vapour;zero for prolonged storage.

2. Very low permeability to gases especiallyoxygen since its interaction leads tochemical and biological deterioration.

3. Aroma barrier property to preserveodours and freedom from external taints.

Table 7.2. Ascorbic acid retention in laminate pouches

Ascorbic acid content value 32.58 mg %40°C 27°C 4°CDays Days Days

14 30 50 14 30 50 65 80 90 14 30 50 65 80 90

Tin plate 25.0 22.7 22.2 26.0 25.0 26.0 25.0 23 22 27.2 26 26 26 24 23PET/Foil/PE 25.0 18.5 15.8 22.1 21.8 15.8 71 43 30 25 24 24.2 24 19 18.6

MET/PET/PE 19.6 31 25 41 39 35 22.2 0 25 22 47 24.7 24.7 22.6 21.0

Package type

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4. Compatibility with the product packed

and also sterilizability with heat,chemicals or radiations.

5. Perfect package and closure integrity.

6. Capacity to form well on operatingmachinery.

7. Provide user convenience for unit andbulk packages.

8. Thermal stability for both low and hightemperature.

9. Sufficiently robust to withstand roughtreatment likely to occur during handlingand transportation.

10. Meet all regulatory specifications.

Package Forms

Aseptically processed foods are packedin varieties of packaging materials andpackage forms. They comprise of flexible,semi-rigid and rigid containers. Aseptic

packages can be divided into the followingmain types:

i. Flexible pouches and bags.

ii. Carton form-fill-seal (FFS) systemssimilar to Tetra Pak and Tetra Brickprinciple.

iii. Thermoform-fill-seal systems fed fromthe reel stock.

iv. Bag-in-box systems.

v. Conventional containers made of glass,tin-plate, etc.

Table 7.3. Effect of oxygen transmission on vitamin retention

Container OTR Ascorbic acidmaterial ml O

2 /m2 retention, %

24h. atm 45 days/26°C

PET/AL-FOIL/CPP 0 92

PET/PE/EVA/PVDC/EVA/PE 1 87

PE/EVA/PVDC/EVA/PE 4 37

BOPP/PVDC/PE 8 31

Fig. 7.1. Asepctically packaged fruit juices

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Hot-Fill-Hold Systems

These are generally used for acid oracidified foods and beverages. Typically theproduct is filled into a container attemperatures of 70-93ºC, sealed and held atthe fill temperature for about 10 minutes forachieving commercial sterility.

The package used for hot-filled processshould be resistant to moisture and heatand withstand the vacuum resulting fromthe condensation of water-vapour in theheadspace once the product is cooled.Conventional metal cans and glass

containers have performed well in hot-fillhold applications.

New package forms which are used for juices, drinks and sauces are pouches madeof composite films, as they should withstandthe heat treatments from both sides of thepouch. Either flat type or stand-up typepouches are used. The material ofconstruction generally is polyester/polyethylene, metallized PET/Polyethyleneor laminates of PET/Aluminium foil/PE,and some co-extruded film structures.

Either HDPE or HD-LDPE combination orpolypropylene can be used as the innermostlayer to provide good thermal resistanceand seal integrity.

Aseptic Packaging in Cartons

The three types of cartons used forpacking liquid foodstuffs are the gable-top,the tetrahedron and the brick shape.

The gable-top type, which is mostly usedfor milk, is made by feeding of the blankfrom a magazine, and the lay-flat tube isthen unfolded and made to enter a mandrel

where the bottom is heated with hot air.The bottom is then folded in accordancewith the score lines, and pressure is appliedfor finishing the bottom sealing. This

rectangular shaped carton is removed from

the mandrel on to a conveyer, filled withliquid and then top sealed. The top seal isperformed with hot air and pressure.

The tetra hedral shaped pouches (TetraPak) are extensively being used foraseptically packed liquid foods. Thetetrahedral shape requires less packagingmaterial than other designs, as it offers themost favourable ratio of area to volume.

For this type of carton, the packagingmaterial is supplied from a reel and passedup to a bending roller and shaped into a

tube with longitudinal made at the ends ofthe carton giving the tetrahedral shape.The process is continuous and results in achain of filled packages. As the seals aremade under the liquid surface, the packageshave no headspace. The transverse sealsare produced by heat and pressure. First,the jaws compress the tube of material thusexcluding liquid from the sealing surface.Secondly, induction heat is supplied,melting and fusing the plastic. Pressure ismaintained while cooling the seal. Theouter plastic cooling is then heated with ashort pulse to ensure that when opening the

jaws, they do not stick to the packagingmaterial and possibly pull the seam apart.

The Brick-Pack System

Rectangular shaped (Tetra Brik) cartonswere introduced around 1963 to facilitatedistribution and have proved very popular.The production of tetra brick-type packagesfrom roll-fed machines follows the sameprinciples as for tetra standard; but thetransverse seams are sealed parallel. The

characteristic brick shape is formed aftercutting off individual packages from thetube, by folding in the flaps and heat-sealingthem.

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Brick-style cartons are currently widelyused for the packaging of high and low aciddrink products. These are essentiallyconstructed of PE/Paper/PE/aluminiumfoil/PE with slight differences amongmanufacturers. Especially for aseptic juiceapplications, the innermost layer is PE-Ionomer co-extruded web as this eliminatesPE delamination from the foil. A pH valueof 4.5 is the critical bench mark of productacidity, determining the utilization of PE/Ionomer layers for products below 4.5 pH.

The outermost polyethylene layerprovides water vapour barrier propertywhile the paper-board provides stiffness,ease of formation on automatic machinesand printability. Aluminium foil ofthickness 0.009 to 0.01 mm affords gas andwater-vapour barrier properties, odourproofness and light protection. Theinnermost web of ionomer (Surlyn) isclaimed to offer 5-10 times more heat-seal(hot tack) strength than ordinary PE,eliminate seal failures and leakers and resistcracking at score lines. The relative amounts

of constituents in the material will beapproximately 71% paper, 22% plastics andthe remaining 7% aluminium. However, ithas been shown that oxygen transmission

rate at the scored area would be 40-50 timeshigher than the flat area.

To eliminate the risk of contaminationfrom the base carton, all edges are protected.Further, as permeation can occur throughraw cut edges of a carton, especially forlong life product, the interior raw edges areeliminated to make the product as close tobeing hermetically sealed as possible.

In the common fin-seal, i.e. polyethyleneto polyethylene layer seal is effected. Anextra strip of plastic overlapping the internal

side of the longitudinal seal (as in Tetrabrick) effectively closes the edges. The othertype is the so-called ‘skiving’ technique,where the inner end of the carton is reducedto one-half of the original thickness, folded

in and sealed to the outer end.

Bag-in-Box Systems

The bag-in-box package utilizes a high-barrier multiplayer bag contained in ashipping container of corrugated fibre-board or wooden box or metal drum. Thecapacity of the bag ranges from about 5litres for institutional use to 250 litres (60gallons) for the industrial market. Even1,135 litres (300 gallon) containers areavailable.

Table 7.4. Oxygen permeation at scored areas

Sl. Material Oxygen transmission rate (cc/m2.24 h)No. Flat area Scored area

1. PE/Paper-board/PE/foil/Ionomer/PE(Aseptic brick type package) 35-40 1500-1520

2. PE/Paper-board/PE/Foil/Ionomer/PE(Hot pack purepack material) 30-35 2000

3. Heat-seal lacquer coated polyester(75 µm) 20-22 20-40

4. Polyester (25 µm) 70-80 70-100

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Smaller bags (5 and 10 l) are generally

made of PE/metallized polyester orpolyamide/PE having four-sides seals ofwidth 5-10 mm. Inclusion of a single web ofinner loose liner of LLDPE often providesadded physical strength.

The outermost polyester or polyamidelayer provides good tensile strength,abrasion resistance and protection to innerfoil web. Aluminium foil of gauges rangingfrom 0.009 to 0.04 mm are used as a barrieragainst water-vapour, gases and volatiles.

The high-barrier structures containingfoil and metallized plastics are susceptiblefor flexure fracture during transportationand handling. The extent of the damagedue to two-crack can be assessed by gelboflexing the packaging material for specificnumbers of cycles and determining thebarrier properties. Metallized films,especially sandwiched between twothermoplastic webs show less effect thanfoils. The effect of flexing on the barrierproperties of some laminates are given inthe Table 7.5.

In the bag design concept, one of theimportant factors is that of spout. The bag innormal use has a welded filament which

contains a rigid plastic spout; it is fitted with

a screw cap or pressed fit cap and sometimeswith spigots for easy dispensing. There aredifferent forms of construction of the spoutswith ability to maintain aseptic condition.

Other Aseptic Systems

Several packaging systems are availablefor packaging foods into formed plastic cups.Most of these systems use FFS-variety wherecups are thermoformed on the packagingmachine from roll stock material. Theconstruction of the cup material is eitherpolystyrene modifications or high barrierplastic forms comprising of PVDC or EVOHresins.

Composite cans have also been used foraseptic packaging, especially for acid foods.

STERILIZATION OFPACKAGING MATERIALS

The surface of the packaging materialmust be completely free of microorganisms

before filling of the food product. Differentmethods are used for achieving sterility –physical processes, chemical sterilants andradiation.

Table 7.5. Effect of flexing on the barrier properties

Sl. Substrate WVTR, g/m2.d OTR, cc/m2.d.atmNo. Flat Flexed Flat Flexed Flexed

(50 - (50 - (100 -times) times) times)

1. Paper/PE/Foil/PE 0.093 4.542 0.326 6014 -

2. Paper/Metallized/OPP 1.736 2.170 52.08 306.9 -

3. Paper/PE/Metallized/ PET 0.449 1.488 1.411 - 4.34

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PHYSICAL PROCESSES

Super Heated Steam System

Metal containers can withstand the hightemperatures involved in this method.Glass containers are also sterilized by steam,but processing times are longer than withcans because common glass bottles cannottolerate the high temperatures. For plasticlaminates, other methods of sterilizationmust be utilized because they cannotwithstand high temperatures. Theadvantage of super-heated steam is that it

can achieve high temperatures atatmospheric pressures. However, it hasbeen shown that microorganisms are moreresistant to superheated steam thansaturated steam.

Dry Hot Air System

Hot air sterilization has advantages anddisadvantages similar to super-heatedsteam. This has been used for a laminate ofthe type paper/foil/PP. Because thetemperature of the air must be low enoughto prevent material destruction, this systemis limited to the packaging of high acidfoods.

PACKAGING OF CARBONATEDSOFT DRINKS

The two major deteriorative changesthat occur in a carbonated soft drink (CSD)are the loss of carbonation and rancidi-fication of essential flavouring oils. Thehydrolytic rancidity could be reduced to alarge extent by the use of high quality rawmaterials and anti-oxidants, and de-

aerating the mix prior to carbonation.Oxidative rancidity could be mitigated bythe effectiveness of the package in providinga barrier to gas permeation.

Conventional Containers

For many years virtually all carbonatedsoft drinks were packaged in glass bottlessealed with crown cork. This closure has ashort skirt with 21 flutes which are crimpedinto locking position on the bottle head.The flutes are angled at 15° in order tomaintain an efficient seal.

In recent years, non-returnable glassbottles are giving way to refillable bottles.These have a foam plastic protective labelor a paper/polyolefin or an all-plastic shrinksleeve, in part as a safety measure to prevent

flying glass fragments in the case ofbreakage of these containers, the crownclosure has been replaced with a roll-onaluminium screw-cup with tamper-prooffacility.

Among the metal containers, the 3-piecetinplate containers have been used sincelong for the packaging of carbonatedbeverages. The highly corrosive nature ofthe contents demands complete protectionof the cans by the use of lacquers. For 3-piece cans, this involves spraying of lacquer

after soldering or welding of side seams.Although tinplate and TFS cans are still

being used to pack carbonated beverages,2-piece aluminium cans predominate themarket. In this, integrity of can lacquer iswell retained. Container weight and designhave been subject of much developmentalwork with the weight of modern can withend down to 18 grams.

It has been reported that cola and lemonbased CSD containing 5-10 ppm aluminiumshowed no sufficient flavour deterioration

after 6 months at 23°C. It has been foundthat corrosion action can be reducedconsiderably by incorporating Mn and Mgin aluminium alloys. Thin walled alumi-

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nium can resists high internal pressure ofCSD.

Among the lacquers, vinyl, epoxy andvinyl organosol coatings have been foundto be compatible with CSD. Epoxy aminehas been found to provide good adhesion,colour, flexibility and freedom from taintingto the product.

Plastic Containers

The factors that influence the selection ofa plastic package intended to contain CSDare indicated in the Figure 7.2. Although

beer is more sensitive to oxygen interaction,soft drinks have a maximum permissiblelevel of 20 ppm for citrus flavoured beveragesand 40 ppm for cola drinks while the water

loss is of the order of 1 percent. Also, the loss

of CO2 through the wall must not be allowed.While increasing thickness will decrease therate of CO

2permeation, the cost therefore, of

the bottle will also increase and acompromise has to be arrived at.

Polyethylene TerephthalateBottles

The polyester, polyethylene terephtha-late (PET) bottles for carbonated beveragessatisfies most of the requirements.Improved blow-moulding techniques andbi-axial stretching have made PET containerto be pressurised due to its strength,dimensional stability and precision. Alsothey have a glass like appearance, goodtransparency, luster, chemical inertnessand unbreakability.

The Advantages of PET Containers

Superior packaging to product ratio,PET container being 63% and 47% moreenergy efficient than glass bottles andaluminium cans, respectively.

Fig. 7.2. Factors to be considered for use of plastic containers for CSD.

PLASTICCONTAINER

FORCSD

Oxygen

Taint

Migration

CO2

Watervapour

Aroma

Fig. 7.3. PET bottles for carbonated soft drinks

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PET bottles are 32% more energy efficient

than glass bottles during delivery of 1,000gallons of soft drinks.

Glass bottles and Al-cans generate 230%and 175% times more atmosphericemissions compared to PET.

PET bottles contribute 68% and 18%less solid waste by weight compared toglass and aluminium containers.

100 kg of oil is required to produce 1,000one litre capacity PET bottles as against

230 kg for 1,000 equivalent glass bottles. PET bottles help in fuel saving due to

their lesser weight.

Currently, more than 90% of PET isconsumed in food packaging withbeverages/drinks forming nearly 80%.

Among other plastic materials suitableto contain CSD, polyethylene naphthanate(PEN) meets several requirements such asphysical, chemical and barrier properties.But it is much more expensive than PET. It

is of importance to note, that diversificationof plastics will make recycling more difficultand hence materials should be specifiedand multilayer structures avoidedwherever possible.

Secondary Packaging

Secondary packaging for beverage packsmay consist of corrugated fibre-board boxes,

shrink wrapping and reusable plastic crates.

In addition to all the technical andcommercial consideration, the issues to beaddressed comprise recycling the usedpackages and the directive to use theminimum amount of packaging possible.

BIBLIOGRAPHY

AIFPA (1996). The Fruit Products. All IndiaFood Preservers’ Association, NewDelhi.

AIFPA (1996). The Standards of Weights

and Measures (Packaged Commodities)Rules, 1977. All India Food Preservers’Association, New Delhi.

Kumar KR, Subramanyan GVS, Swamy MNand Naresh R (1985). Changes in fruit

juice packed in flexible and rigidcontainers. National Symposium onRecent Development in Food Packaging,AFST(I), Mysore.

Prasad PVS (2001). Recycling of PET waste.In: Proceedings of Intl. Confe-rence onPlastics Waste Management andEnvironment, ed: V.P.Malhotra. ShriramInst for Industrial Research, Delhi.

Seshadri KS, Gowramma RV, MahadeviahM, Kumar KR and Pandian SM (1994).Packaging of mango juice in flexiblepackaging materials. Indian FoodPacker, 48(3): 25-29.

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